Rugby league star Benji Marshall looks set to complete a high-profile switch to union at the end of the season after it was confirmed he has asked to be released from his current contract with NRL side the Wests Tigers.

Marshall, 28, shocked the Tigers on Monday night by demanding to be released from the final two years of his contract after failing to agree terms on an upgraded deal. A star of the 13-man code for over a decade who also helped guide New Zealand to the World Cup crown in 2008, Marshall has already been linked to the Auckland-based Blues and the Sydney-based Waratahs.

Marshall's manager Martin Tauber said a breakdown in negotiations over a new contract was the reason for the decision. Marshall is believed to have had a handshake agreement with Tigers' former CEO Stephen Humphreys for an upgraded and extended contract through to the end of 2017. But this became unclear when Humphreys stood down two months ago.

"He's given 13 years of his life to the club and he needs a change," Tauber told Fox Sports. "The protracted negotiations began in January and here we are in July and we still don't have a firm and fixed agreement. We've had handshake deals that under the previous CEO that never eventuated before he resigned and that hasn't been fulfilled. I understand that business is business and the club have still given us what is still a very healthy offer but Benji has made his decision."

Tigers acting CEO Grant Mayer said he was caught unawares when he was told of Marshall's decision, adding a release is unlikely to be granted until the club's board meet later this week. "We were very, very confident that we were headed in the right direction with Benji but the phone call last night was surprising," said Mayer. "But I can understand the reasons Benji made the decision."

The Blues were the first side to be linked with a move for the highly-regarded player but coach Sir John Kirwan has warned Marshall that he may be forced to take a pay cut due to the limited budget available.

The Waratahs have also expressed an interest in Marshall but financial concerns mean he would have to commit his international future to the Wallabies in order to attract a contract top-up from the Australian Rugby Union - something he reportedly does not want to do. Earlier this month, he said: ''Growing up, it was a dream of mine to play for the All Blacks. That changed and I started playing rugby league. But I'll consider rugby, absolutely.''

A move to union appears the only likely due to Marshall's reluctance to sign for any of the Tigers' NRL rivals. "'Benji has always stated that he would not play for another rugby league club, as he felt great thanks to all the sponsors who have supported him, and the fan base who have always cheered him on," said Tauber.

Given the financial restraints on some, a move to Japan or even Europe would also appear to be an option for Marshall but playing overseas would make him ineligible for All Blacks honours due to their current selection policy or only selecting New Zealand-based players.

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